The invention relates to a motor-pump unit for a high-pressure cleaning appliance with an electric motor having a motor housing, on the outside of which a cooling channel is arranged, and with a pump driven by the electric motor and having a suction inlet for taking in liquid to be pressurized and a pressure outlet for discharging pressurized liquid, liquid to be pressurized being fed by way of the cooling channel to the suction inlet.
By means of such motor-pump units, a cleaning liquid, preferably water, can be pressurized and subsequently directed at an article to be cleaned. For this purpose, in particular, a high-pressure hose carrying, for example, a spray gun or a spray lance at its free end can be connected to the pressure outlet of the pump.
The electric motor is often cooled by a flow of air which is preferably directed past the exterior of the motor housing. However, this requires considerable heat exchanger surfaces and so air cooling is only possible with spatially extended motor-pump units.
In DE 81 11 792 U1, it is proposed that liquid cooling be provided for the electric motor in addition to air cooling. A steel pipe helically surrounding the stator of the electric motor is embedded for this purpose in the housing wall of the motor housing. However, the embedding of a steel pipe in the housing wall of the motor housing requires considerable production expenditure and involves substantial costs.
In DE 35 45 665 C2, it is proposed that the motor housing be constructed in the shape of a pot and a plastic hood also configured in the shape of a pot be placed on the motor housing to form a cavity between the motor housing and the plastic hood. Cooling liquid can be fed by way of an inlet connector to the cavity. The cooling liquid can be discharged from the cavity by way of an outlet connector and then fed to the suction inlet. In such a configuration, the motor housing is surrounded by cooling liquid and so the electric motor can be effectively cooled without provision of a flow of air and can, consequently, be of compact design. However, the provision of the cavity for the cooling liquid requires an additional plastic hood, which has to be placed on the motor housing in an additional assembly step.
The object of the present invention is to so develop a motor-pump unit of the kind mentioned at the outset that it can be produced and assembled more cost-effectively.